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Gerda Strutzenberger Tobias Wunsch Josef Kroell Jacqueline Dastl Hermann Schwameder 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):97-108
Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0–1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect. 相似文献
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通过研究非单调轴类零件工艺与编程加工过程,介绍了利用 FANUC 0I Mate-TC 数控系统提供的宏程序编程功能编制出的具有通用性、适用性且应用简单的数控程序,分析了使用自动编程软件编程时工件的加工工艺。通过实践检验,手工编程和自动编程相结合优化了工艺方案,提高产品的尺寸精度和生产效率。 相似文献
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This study addresses heat transfer performance of various configurations of coiled non-circular tubes, e.g., in-plane spiral ducts, helical spiral ducts, and conical spiral ducts. The laminar flow of a Newtonian fluid in helical coils made of square cross section tubes is simulated using the computational fluid dynamic approach. The effects of tube Reynolds number, fluid Prandtl number, coil diameter, etc., are quantified and discussed. Both constant wall temperature and constant heat flux conditions are simulated. The effect of in-plane coil versus a cylindrical design of constant coil, as well as a conical coil design is discussed. Results are compared with those for a straight square tube of the same length as that used to form the coils. Advantages and limitations of using coiled tubes are discussed in light of the numerical results. 相似文献
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文章分析非圆齿轮的结构参数特征,完成了非圆齿轮的3D设计,利用SolidWorks软件建立非圆齿轮的三维模型,并生成STL文件,最后采用3D打印技术打印出非圆齿轮。文章提出的方法与实验为非圆齿轮的智能加工提供了新思路。 相似文献
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